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Basis for original (SCP) IDLH: No useful data on acute inhalation toxicity are available on which to base the IDLH for nitric oxide. The chosen IDLH, therefore, is based on the statement by Sax [1975] that 100 to 150 ppm oxides of nitrogen are dangerous for short exposures of 30 to 60 minutes. The chosen IDLH seems reasonable because NIOSH [1976] cited a rabbit 15-minute LC50 of 315 ppm for nitric oxide [Carson et al. 1962].

Short-term exposure guidelines: None developed

ACUTE TOXICITY DATA:

Lethal concentration data:

Species

Reference

LC50 (ppm)

LCLo (ppm)

Time

Adjusted 0.5-hr

LC (CF)

Derived value

Rabbit

Mouse

Rat

Mouse

Carson et al. 1962

Flury and Zernik 1931

Ivanov and Szubaev 1979

Pflesser 1935

315

-----

854

320

-----

2,500

-----

-----

15 min

12 min

4 hr

?

249 ppm (0.79)

1,850 ppm (0.74)

1,709 ppm (2.0)

?

25 ppm

185 ppm

171 ppm

?

Other animal data: Guinea pigs have survived an exposure at 175 ppm for an unstated period [Bodansky 1951].

Human data: It has been stated that exposures to oxides of nitrogen between 100 and 150 ppm are dangerous for exposures of 30 to 60 minutes [Sax 1975].

Revised IDLH: 100 ppm [Unchanged]

Basis for revised IDLH: Based on acute inhalation toxicity data in humans [Sax 1975], the original IDLH for nitric oxide (100 ppm) is not being revised at this time.